Clean and peel 500 g leeks. Instead of slicing straight across, cut them on the diagonal.
2: Steam the leeks: the best way is to use a steamer basket so they sit just above the water, not in contact with it, and put the pan on high heat.
3: Cook uncovered and keep an eye on both their texture and colour - they should stay nice and green and still have a little "bite". Please note that we don't salt them when steaming.
4: Melt 30 g butter in a large frying pan on medium heat. When sizzling, add the leeks, salt and pepper and cook in this second stage for just 2 or 3 minutes, stirring frequently. Check the seasoning, then keep hot.
6: Whisk frequently and for a good while over the bain-marie...
7: ...until it reaches the classic sabayon texture. Finish by checking the seasoning. Note: to be sure your sabayon will work, you can also follow the tips in this recipe for sabayon.
8: This is best served in individual hot dishes. Arrange a layer of leeks and pour the sabayon over. Finish with a little freshly ground pepper.
Remarks
Of course, if you have jus from another type of mushrooms, this will also work well. For a more delicate flavour, replace 1/3 of the mushroom jus with the same volume of Vin Jaune - it's superb! (if you like Vin Jaune, that is...).